Various types of objects are molded which are provided with apertures or bores therein. Typically, these objects are formed using relatively simple, two-piece dies which are mounted in a molding machine, such as an injection molding apparatus, such that the die portions are opened and closed along a straight line. After the molding process is completed, the object is removed from the mold and the necessary bores or apertures are then formed in the object by a subsequent machine operation, as by punching, drilling, etc. This further machine step obviously adds to production costs in terms of labor and is to be avoided if possible.
Others have attempted to devise mold assemblies in which an aperture is molded into the object, however, these prior efforts have involved mold assemblies having three or more separable parts and wherein the fluent molding material is not forced into the mold under high pressure, as in injection molding. The use of mold assemblies having more than two parts is undesirable due to tooling and production costs, moreover, such complicated mold assemblies are incompatible for use in some molding machines such as injection molding apparatus where high productivity is an important goal.
Heretofore, it has not been possible to injection mold an aperture in an object using injection molding techniques, where the axis to the aperture is perpendicular to the line of separation of the die parts. This is a result of the fact that the fluent molding material is forced under high pressure into the mold assembly, and as result of the pressure, the fluent material is forced between portions of the core which is intended to form the aperture; consequently, a thin layer of flashing is formed over the aperture and must therefore be removed in a subsequent machine operation.
There is therefore a clear need in the art for a relatively simple, two-piece mold assembly for forming an object having an aperture therein, wherein the central axis of the aperture extends generally perpendicular to the line of separation of the molds die parts. The present invention meets this need and is therefore responsible for substantially increasing production efficiency and reducing tooling and costs.